I actually have to confess to cursing dams generally, specifically, and completely as recently as last January as I was riding in the back of a van with two Chinese colleagues to the Shanghai airport. I feel warm and sympathetic to this slightly younger and more idealistic version of myself. After all, dams have ruined a lot of rivers globally, and the U.S. has until very recently been the world’s leader in building very large and destructive dams. In many large coastal U.S. states, there may be only one or two large rivers that lack a dam. I remember how beautiful and biologically rich was the first such river in Texas I saw a few years ago (the Devil’s River; I was visiting a TNC property at the time). It is the last undammed river in Texas. Alaska is the only U.S. state with significant numbers of undammed rivers. Indeed, until very recently the U.S. has effectively “owned” most of the really big dams in the world (as seen on this map of about 1 percent of the medium and large dams of the world). China is making great strides to overtake the U.S. But other countries are working hard on this project as well.

Dams are an ancient form of transforming the landscape by humans. Some of the oldest in the world date back about 5,000 years in places like Yemen, Syria, and Turkey. Some of these are still functioning or have failed only in recent centuries. Thinking more broadly than simple storage dams (traditionally used for irrigation purposes in arid regions), humans have been modifying freshwater ecosystems significantly for extremely long periods of time — one recent study suggests wetlands have been modified for rice growing in China for about 8,000 years. One might say that to dam is human. Thus, if we are to damn dams, we are damning some very old and deep part of ourselves.

A reasonable criticism of this sentiment is that the modern of era of dam-building is quite different. We can date this period to the late 18th and early 19th century and the English and Scottish engineers who began building ever-larger dams. From this tradition, dams are beautiful things, a vision of ourselves and our force and power upon the landscape. Taken solely in these terms, I can appreciate this point of view. Today, somewhere between 45,000 and 55,000 medium to large dams dot our landscape, not to mention (what is no doubt many times more) irrigation canals, hydropower facilities, flood dykes, cooling ponds, and the many other kinds of water-body modifications humans apparently revel in. I was recently struck by how similar Matto Grosso state in southwestern Brazil looks like my native Texas from the air: thousands of small cattle tanks in fields and barrages across creeks. Once we get to this small scale of freshwater modification, regulated almost noplace on the planet, our impact on water and water management appears obviously enormous. However, I am not limited to this point of view. I have other frames of reference.

Managing water means managing all of the species that depend for at least some part of their life cycle on that water. Most modifications are attempts to regularize flows between hard rains and harder droughts. But this results in a kind of ecosystem engineering, selectively picking some species as winners and losers. It’s not a very nice way of being neighborly with your fellow non-humans. And ultimately this has been the basis of my negative and instinctive response to dams. The current salmon crisis in the U.S. Pacific Northwest is in no small part a result of more than a century of massive river modification through big dams.

So what changed in me? How did I reconcile? Perhaps the first change was hearing a water infrastructure economist (I’ll call him J) argue forcefully that saying no to all modifications is the fastest way possible to exclude yourself from any kind of influence with the important institutions that are interested in building or financing dams. The second point was when J pointed out that not all dams are created equally. Storage dams like Three Gorges or the Hoover dam are massive entities designed to retain a lot of water for long periods of time. A barrage in contrast is more of a comma or an ellipsis than a period or paragraph mark; the water builds up or pools but is not actually stopped or stored. A run of the river dam (increasingly common for hydropower) diverts some part of a river into a pipe or canal and (in theory) doesn’t effect the main body of the river; after spinning a turbine, the pipe takes the water back to the river. I can now say with more precision that I am not crazy about storage dams in particular. Other dams ... I am willing to consider, under certain conditions, and with careful implementation.

Moreover, there’s the issue of how you run dams. In the past, dams were only operated for the benefit of their primary human consumers. The environmental flows movement (“e-flows”) however is an attempt to make dams release water in a manner more similar to natural river flows (in a much simplified definition). The idea sounds great: you can begin to mimic some of the ecosystem processes by overregulation of flow regimes by storage dams. But the practice has been mostly limited to the U.S. and Europe so far. The idea is spreading, and implementation is getting more sophisticated in many countries.

In the 1980s, we mostly said: dam or no dam. Now we have a range of arguments to make. Why not a series of RoR dams? Why not put all of our dams on this tributary and leave this other one alone? Why can’t we design climate-aware e-flows management regimes?

My conclusion:

Extremism in defense in rivers may be no vice, but it doesn’t seem to really do any good either.

My apologies to Barry Goldwater for that.

Perhaps J’s most important lesson to me was simply that we — the conservation community — need to be able to engage in a conversation about how and where water infrastructure is placed. If nothing else, we may be able to adjust when it is deployed. Climate change is a very forceful argument for that approach in particular. Mostly my re-think is about changing the terms of the debate with people that don’t care very much about bugs or native fish or freshwater molluscs to ecosystem services, habitat protection, and ecological health that is tired to human economic well being. If that means that we need to use more complicated arguments that might also be more effective, so be it.

Tags: Dams, policy, conservation